The best known art to the present invention known to me is my prior U.S. Pat. No. 3,596,764 and the prior art patents cited therein namely U.S. Pat. Nos. 49,370; 637,342; 643,740; 798,596; 976,811; 1,316,058; 3,458,981; and English Pat. No. 16.944 of 1891.